Protective Cap for a Positive Crankcase Ventilation Port and a Method to Manufacture

ABSTRACT

A positive crankcase ventilation system for an internal combustion engine routes blowby gases into the intake of the engine. Because the blowby gases have about 12% water vapor, during cold-weather operation, the water vapor may freeze in the PCV valve or in the port that couples the PCV duct with the intake manifold. In situations in which the PCV duct is pointing toward the direction of flow of the intake gases, a hood or cap is placed over the end of the tube according to the present disclosure. It can be as simple as a 90-degree elbow or multiple openings in the cap. A centerline of the openings is perpendicular or at an obtuse angle with respect to the direction of flow in the duct so that the intake gases do not directly access the openings and cause freezing in the openings (or ports).

FIELD

The present disclosure relates to positive crankcase ventilation systemsin internal combustion engines, in particular the port in the intakesystem through which blowby gases flow.

BACKGROUND

A positive crankcase ventilation (PCV) system for an internal combustionengine is shown in FIG. 1. An internal combustion engine 10 has acrankcase 12 with oil 14 in an oil pan. Oil mist is formed by thecrankshaft 16 having connecting rods coupled thereto. An oil mist formsin the crankcase due to oil flying off of rotating components. A smallportion of combustion gases in combustion chamber 50 pass by piston 20into crankcase 12. The blowby gases pick up oil mist. Rather thanventing these gases to the atmosphere, they are routed into thecombustion chamber to be burned. Crankcase 12 is in fluid communicationwith a volume above the valvetrain of a cylinder head 24. Engine 10 is avee engine with two cylinder banks. A PCV valve 26 is provided in one ofthe banks. A PCV duct 28 couples between PCV valve 26 and intakemanifold 44. PCV duct 28 has a port 30 where it couples to intakemanifold 44. Fresh air is inducted into engine 10 via an intake duct 40that has a throttle valve 42 disposed therein. Fresh gases are providedto intake manifold 44 and mix with blowby gases from the PCV duct beforeentering combustion chamber 50.

Blowby gases are predominantly exhaust gases, which containapproximately 12% water vapor. During cold weather operation, the watervapor can freeze in the PCV system interfering with proper operation. Itis known to use heating elements to avoid freezing of the PCV valve,such as described in U.S. Pat. No. 6,546,921. Additionally, the watercan freeze in port 30, i.e., the port through which the blowby gasesenter into the intake manifold for mixing with the fresh air. Port 30 inFIG. 1 is positioned on the wall of intake manifold 44. To encouragemixing, duct 28 is often extended into manifold 44 so that port 30 isnearer the center of manifold 44. In such a configuration, the flow ofthe gases is into port 30. When a lot of fresh, cold air flows past theport, the water vapor freezes in the port obstructing the flow.

SUMMARY

In many PCV duct installations into an intake manifold, the port of theduct is not subjected to oncoming fresh intake gases, which when coldcan freeze in the duct and negatively impact PCV operation. However,some engine packages place constraints that force the PCV port into theoncoming gases. To overcome the potential for freezing a cap is placedon the end of the duct. The cap closes off the top of the duct andprovides openings in the side surface of the cap.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a PCV system for an internal combustionengine;

FIGS. 2 and 13 are illustrations of an intake manifold having a PCV portwith a cap over the PCV port according to an embodiment of thedisclosure;

FIG. 3 shows an outer wall of the intake manifold of FIG. 2;

FIG. 4 is a view of an embodiment of an outer PCV duct;

FIG. 5 is a view of a lower shell of the intake manifold of FIG. 2;

FIGS. 6 and 7 are a close up view and a cross-sectional view of aportion of the intake manifold of FIG. 2;

FIGS. 8-11 are alternative embodiments for an inner PCV duct; and

FIGS. 12 and 14 are flowcharts showing process by which intake manifoldsaccording to embodiments of the disclosure are fabricated.

DETAILED DESCRIPTION

As those of ordinary skill in the art will understand, various featuresof the embodiments illustrated and described with reference to any oneof the Figures may be combined with features illustrated in one or moreother Figures to produce alternative embodiments that are not explicitlyillustrated or described. The combinations of features illustratedprovide representative embodiments for typical applications. However,various combinations and modifications of the features consistent withthe teachings of the present disclosure may be desired for particularapplications or implementations. Those of ordinary skill in the art mayrecognize similar applications or implementations whether or notexplicitly described or illustrated.

In FIG. 2, an intake manifold 60 is comprised of an upper shell 62 and alower shell 64. In the view in FIG. 2, mostly upper shell 62 is visible.A cutout of upper shell 62 is shown in the vicinity of the a PCV duct toprovide a view of this element. Lower shell 64 is partially visiblethrough the cut out. Fresh gases enter manifold 60 through inlet 70 inthe direction shown by arrow 90 and then turns as shown by arrow 92. Airis then delivered to four runners 74 to feed four cylinders as shown byarrows 94. Blowby gases flow into an outer PCV duct 80 via a PCV valveand a tube (not shown). Outer PCV duct 80 has a barb 86 for coupling tothe tube. An inner PCV duct 82 extends into manifold 60 to depositblowby gases into the intake flow. In the embodiment shown in FIG. 2,inner PCV duct has a cap 84. In this example, cap 84 is an elbow at theend of duct 82. Cap 84 has an opening 86, the centerline of which isperpendicular to a centerline of duct 82. It has been found that as longas the flow of fresh intake gases is not pointed directly at the openingof the PCV port, freezing or exhaust water vapor is sufficientlylessened.

In many situations, the PCV duct can be arranged within the intakemanifold such that the flow of fresh gases does not impinge directlyonto the port of the PCV duct. However, in the example shown in FIG. 2,due to packaging and the layout of the intake manifold, the only placeavailable for an inner PCV duct is directly into the intake flow.

FIG. 3 shows a portion of lower shell 64 of the intake manifold. Thewall of lower shell 64 has an orifice 102 to which outer PCV duct (notshown) fluidly couples. In FIG. 4, outer PCV duct 80 includes a flange106. In some embodiments, main intake manifold housing 80 of FIG. 3 is aplastic that includes carbon black. Duct 80 and flange 106 are made ofthe same or a similar plastic as lower shell 64, except with no carbonblack. Referring back to FIG. 3, a flange 108 on the wall of lower shell64 that includes a weld bead 104 that surrounds orifice 102. A laser isused to weld flange 106 of outer PCV duct via a weld bead 104 on housing100. The laser beam is largely transmitted through flange 106 that hasno carbon black and is aimed at weld bead 104, which absorbs the laserenergy and melts. When weld bead 104 cools, a seal is formed betweenflange 106 of duct 80 and housing 100.

A lower shell 64 has inlet 70 and leads to the inside of runner 75 thatleads to intake ports of an engine (not shown). Outer PCV duct 80couples to lower shell 64 and inner PCV duct 85 is held in place inlower shell 64. Greater detail of the coupling of ducts 80 and 82 withlower shell is shown in a cross-sectional, blowup in FIG. 6. Outer PCVduct 80 has flange 106 that sits against flange 108 of lower shell 64.Inner PCV duct 82 has a cap 85 that is an elbow or, alternatively, atee. Inner PCV duct 82 is assembled by inserting cap end 85 into theorifice in lower shell 64. Inner PCV duct 82 doesn't fall through theorifice due to a shoulder no that extends outwardly from inner PCV duct82 that engages with a shoulder 112 of lower shell 64. In someembodiments, inner PCV duct 82 is not affixed with lower shell 64; it issimply press fit against shoulder 112. A seal is provided by a laser, orother, weld between flange 106 of outer PCV duct 80 and flange 108 oflower shell 64. In FIG. 7, a cross-sectional view of portions of the PCVducts and lower shell 74 is shown. Flange 108 additionally has a keyway124 into which a key 120 of inner PCV duct 8 engages (only key 120 ofinner PCV duct 82 is visible in FIG. 7). By engaging key 120 into keyway124, inner duct 82 is indexed so that a desired position of inner PCVduct 82 is ensured so that the cap is positioned in a desired andrepeatable configuration.

In the embodiment shown in FIGS. 2-7, PCV ducts 80 and 82 are separatelyformed from lower shell 64 and then assembled. Alternatively, the innerand outer PCV ducts are integrally molded with the lower shell of theintake manifold. A cap is molded separately before being affixed to thetip of the internal portion of the PCV duct. The elbow embodiment ofduct 82 is a possible configuration for such an embodiment. Additionalalternatives are shown in FIGS. 8-11. In FIG. 8, a portion of a straightduct 200, i.e., a portion of the inner PCV duct, has a centerline 202. Acap 210 has four openings 214, one in the center in the view in FIG. 8,one directly behind the one centered in the view and one upper and onelower. A centerline 212 of the upper and lower openings is perpendicularto centerline 202 of duct 200. Cap 210 has a cover 216 so that freshintake flow as shown in FIG. 8 by arrow 220 is prevented from directlyentering duct 200, but instead enters via openings 212. In an embodimentin FIG. 9, a cap 230 has eight openings around the periphery of the cap.Openings 230 at the top and the bottom have a centerline 232 that isperpendicular with centerline 202 of duct 200. All of openings 230 havecenterlines that are substantially perpendicular to centerline 202. Inthe interest of simplicity in FIG. 9, they are not all illustrated. Cap230 has a conical cap 236 coming to a point 238. There may be someadvantage to conical cap 236 in directing intake air flow (arrow 220)around the obstruction that cap 230 and duct 200 present. In FIG. 10,cap 240 is a tee section coupled to duct 200. A central axis 242 throughopenings 244 is perpendicular to centerline 202. The arms of tee 240 canbe shortened to present less of an obstruction within the intakemanifold.

The embodiments in FIGS. 8-10 show centerlines of the openingsperpendicular to the centerline of duct 200. For even greater protectionfrom freezing, the holes can be tucked up under the cap, as shown inFIG. 11. Cap 250 has a plurality of openings 254 that are protected bythe widest portion of cap 250. A centerline 262 of one of the openings254 forms an obtuse angle 270 with a centerline of 202 of duct 200. Acenterline of duct 200, which is shown by direction of flow of arrow 260forms an angle greater than 90 degrees with respect to a centerline ofopening 254.

In FIG. 12, a method to fabricate a portion of an intake manifold isshown. In blocks 300, 302, 304 and 306, the lower shell, the inner PCVduct, the outer PCV duct, and the upper shell, respectively, areinjection molded or formed by any suitable method. The lower shell hasan orifice for a PCV duct, weld bead on the outer surface of the housingsurrounding the orifice, a shoulder to capture the inner PCV duct. Inblock 308, the inner PCV duct is rotated so that the key of the ductengages with the keyway of the lower shell. In block 312, the outer PCVduct is laser welded onto the outer PCV duct on a flange of the lowershell of the intake manifold. The outer PCV duct is made of the same, orsimilar, plastic as the housing and the inner PCV duct except that theouter PCV duct and housing have carbon black and the outer PCV duct doesnot. A laser is used to heat up the weld beam, after passing through theflange on the outer PCV duct. In block 314, the lower shell is frictionwelded to the upper shell.

In an alternative embodiment in FIG. 13 a lower shell 400 has an outerPCV duct 410 and an inner PCV duct 412 that are molded in a unitarypiece with lower shell 400. A pin can be pulled to formed the inside ofducts 410 and 420 and an orifice through the wall of lower shell 400. InFIG. 13, a cap 414 is shown separate from duct 422. The cap 414 is to becoupled to duct 412 with a tip 422 of duct 412 coupling to a surface 424of cap 414. Cap 414 and duct 412 can be coupled via friction welding,spin welding, sonic welding, ultrasonic welding, and an adhesive. Cap414 is a tee. Other cap configurations, such as an elbow or examplesshown in FIGS. 8, 9, and 11, or any other suitable alternatives may besubstituted for the tee.

In FIG. 14, the lower shell of the intake manifold, the cap for the tipof the inner PCV duct, and the upper shell of the intake manifold areinjection molded in blocks 320, 322, and 326, respectively. The lowershell has a unitary PCV duct that extends therethrough, including theinner PCV duct and lower PCV duct. In block 328 the cap is coupled onthe inner end of the PCV duct by any suitable technique such as sonicwelding, spin welding, friction welding, and applying an adhesive. Inblock 330, the upper shell of the manifold is welded to the lower shellof the manifold, or affixed and sealed in any suitable manner.

While the best mode has been described in detail with respect toparticular embodiments, those familiar with the art will recognizevarious alternative designs and embodiments within the scope of thefollowing claims. While various embodiments may have been described asproviding advantages or being preferred over other embodiments withrespect to one or more desired characteristics, as one skilled in theart is aware, one or more characteristics may be compromised to achievedesired system attributes, which depend on the specific application andimplementation. These attributes include, but are not limited to: cost,strength, durability, life cycle cost, marketability, appearance,packaging, size, serviceability, weight, manufacturability, ease ofassembly, etc. The embodiments described herein that are characterizedas less desirable than other embodiments or prior art implementationswith respect to one or more characteristics are not outside the scope ofthe disclosure and may be desirable for particular applications.

1-11. (canceled)
 12. A method to fabricate an intake manifold,comprising: molding a first shell of an intake manifold with an integralPCV duct extending therethrough; molding a cap having a plurality ofopenings; and affixing the cap on an inner tip of the PCV duct wherein acenterline of the openings is offset from a centerline of the PCV duct.13. The method of claim 12, further comprising: molding a second shellof an intake manifold; and affixing the first shell to the second shell.14. A method to fabricate an intake manifold, comprising: molding afirst shell of an intake manifold with an orifice; molding an inner PCVduct having a cap on a downstream end of the duct; molding an outer PCVduct; placing the inner PCV duct in the orifice; and welding the outerPCV duct onto the first shell.
 15. The method of claim 14 wherein thecap is occluded in a direction along the duct and has at least oneorifice; and a center of the at least one orifice is offset from acenterline of the inner PCV duct.
 16. The method of claim 14, furthercomprising: molding a second shell of an intake manifold; and affixingthe first shell to the second shell.
 17. The method of claim 14 whereinthe first shell has a keyway and the inner PCV duct has a key, themethod further comprising: engaging the key into the keyway.
 18. Themethod of claim 14 wherein: the first shell has a flange with a weldbead surrounding the orifice; the outer PCV duct has a flange; the firstshell is comprised of a material containing carbon black; and the outerPCV duct is comprised of a material that transmits laser light, themethod further comprising: laser welding the flange of the outer PCVduct onto the flange of the first shell.
 19. The method of claim 14wherein: the first shell has a shoulder proximate the orifice; and theinner PCV duct has a shoulder, the method further comprising: engagingthe shoulder of the inner PCV duct with the shoulder of the first shellprior to welding the outer PCV duct onto the first shell.
 20. The methodof claim 14 wherein the outer PCV duct contains a barb.
 21. A method tofabricate an intake manifold, comprising: molding first and secondshells of an intake manifold, the first shell having an orifice definedtherein; molding an inner PCV duct having a cap on a downstream end ofthe duct; molding an outer PCV duct; placing the inner PCV duct in theorifice; welding the outer PCV duct onto the first shell; and weldingthe first shell onto the second shell.
 22. The method of claim 21wherein: the inner PCV duct defines a cylinder therein; the cap occludesthe cylinder defined by the inner PCV duct; a plurality of openings isdefined in the cap; and the openings are offset from the cylinderdefined by the inner PCV duct.
 23. The method of claim 21 wherein: thecap is a short duct that forms a tee with the inner PCV duct; and acenterline of the short duct of the cap is perpendicular to a centerlineof the inner PCV duct.
 24. The method of claim 21 wherein: the capoccludes the cylinder defined by the inner PCV duct; a plurality ofopenings is defined in the cap; and flow through the inner PCV duct iscaused to turn when flowing from the inner PCV duct through one of theplurality of openings.
 25. The method of claim 21 wherein: the cap isoccluded in a direction along the duct; the cap defines at least oneopening; and a centerline of each opening is offset from a centerline ofthe inner PCV duct.
 26. The method of claim 21 wherein the first shellhas a keyway proximate the orifice and the inner PCV duct has a key, themethod further comprising: engaging the key into the keyway.
 27. Themethod of claim 21 wherein: the first shell has a flange with a weldbead surrounding the orifice; the outer PCV duct has a flange; the firstshell is comprised of a material containing carbon black; and the outerPCV duct is comprised of a material that transmits laser light, themethod further comprising: laser welding the flange of the outer PCVduct onto the flange of the first shell.
 28. The method of claim 21: thefirst shell has a shoulder proximate the orifice; and the inner PCV ducthas a shoulder, the method further comprising: engaging the shoulder ofthe inner PCV duct with the shoulder of the first shell prior to weldingthe outer PCV duct onto the first shell.
 29. The method of claim 21wherein the inner PCV duct is comprised of a duct portion and a cap, themethod further comprising: welding the duct portion to the cap.
 30. Themethod of claim 21 wherein the outer PCV duct has a circumferential barbthat extends outwardly from an outer surface of the outer PCV duct.